BCC,

Hopefully these screenshots shold give you a start.

You'll need to add expressions to the Send Mail task which will reference existing variables.

You can test your expressions for syntax errors by clicking the 'Evaluate Expression' button; if you have values assigned to your variables you will see them in the evaluated expression.

Something I find handy is to use BIDS Helper (download from http://bidshelper.codeplex.com) which will place a coloured triangle in the top lefthand corner of any task that uses expressions. That way you can see at a glance whether expressions are being used in a package. It does the same thing (albeit a different colour) for Connection Managers.